Conventionally, there is known a robot having a function for teaching the position of a target object such as a semiconductor wafer or a glass wafer.
For example, a robot disclosed in Patent Literature 1 includes a first arm member rotatably attached to a base body, a second arm member having a base end portion attached to the tip end portion of the first arm member such that the second arm member is rotatable, and a hand rotatably attached to the tip end portion of the second arm member. The first arm member is driven to be rotated by a first arm drive means, the second arm member is driven to be rotated by a second arm drive means, and the hand is driven to be rotated by a wrist shaft drive means including a servo motor. In a state in which a control loop gain of the wrist shaft drive means is set to substantially zero, the hand is brought into contact with a target object, thereby the angular position of a wrist shaft fixedly attached to the hand is changed, and the changed angular position of the wrist shaft is detected by an encoder of the servo motor. Based on shape data and dimension data of the hand which are stored in a memory unit, the posture of a robot arm and the angular position of the wrist shaft, at a time point when the hand contacts the target object, the position of the target object within an X-Y flat plane is determined.
A robot disclosed in Patent Literature 2 is provided with a wrist having a horizontal flexibility on the tip end portion of an arm. This wrist is provided with a hand having contact portions. The contact portions include a first inclined portion which is formed on a portion (wrist portion) of the hand, the portion being closer to a wrist shaft than a support portion supporting a wafer is in such a manner that the first inclined portion is inclined toward one side in the circumferential direction of the wrist shaft as the first inclined portion is away from the wrist shaft, and a second inclined portion which is formed at the support portion in such a manner that the second inclined portion is inclined toward the other side in the circumferential direction of the wrist shaft as it is more distant from the wrist shaft, and is continuous with the first inclined portion. In a state in which the contact portion is in contact with the target object, the tip end portion of the arm is moved, the position of the target object in the state in which the contact portion is in contact with the target object, is taken-in, and the position of the target object is detected based on a value in a state in which the target object is located in a portion at which the first inclined portion and the second inclined portion are continuous with each other.